This invention is related broadly to apparatus for reconditioning printer ribbons, and specifically to an improved re-inking apparatus for such ribbons having a recirculation system for the re-inking composition.
Apparatus for re-inking printer ribbons is known in the art, and basically comprises a feed roller, quide rollers, take-up roller, and inking fountain. Also, some means is provided to set or adjust the feed rate of the re-inking composition by the fountain. This is helpful when re-inking computer printer ribbons where, because of their width, different flow rates along the width of the ribbon can result in an uneven coat of fresh ink. Generally, the adjustment means is some means which adjust the gap between the ductor and inking rollers which make up the inking fountain.
The re-inking composition used in re-inking ribbons generally, and computer printer ribbons specifically, is normally a carbon composition in the form of fine carbon particles dispersed in a relatively volatile liquid vehicle. After the re-inking composition is coated on the ribbon, the vehicle evaporates from the composition and leaves a fresh coating of the carbon composition on the "re-inked" ribbon.
In the re-inking process, the ductor roller rotates in an open container or reservoir containing a supply of the re-inking composition. The ductor roller picks up an amount of the composition on its surface and transfers some to the inking roller which is in rolling contact with the ribbon. In turn, the inking roller transfers an amount of the composition to the ribbon to coat or "re-ink" it.
In order to keep the carbon composition from settling out, the re-inking composition was circulated by pumping it from the reservoir and then back again. In addition, means was provided to filter the composition as it was recirculated in order to keep the re-inking composition free from contaminates. Filtration and recirculation are desirable when re-inking computer prints ribbons because they tend to have paper particles on their surface which become punched out of the paper on which the computer output is printed by the printing hammers of the computer printers. Such particles fall from the ribbon into the ink supply during re-inking and, if not filtered out, may be picked up and deposited on the re-inked ribbon.
While the use of an open container as the supply for the ink composition does not render the re-inking apparatus inoperative, it does present problems. The open container provides an opportunity for the vehicle in the re-inking composition to evaporate which results in a thickening of the composition. The feed of this composition depends to some extent on the surface tension of the composition, which is related to its viscosity or "thickness". A change in the viscosity or "thickening" of the composition results in a change of the rate of feed of the composition. This problem is further complicated by the fact that enough re-inking composition must be kept in the reservoir to provide a continuous supply along the length of the ductor roll and in doing so the re-inking composition tends to not move or to stagnate and allows for further evaporation. Still further, the size of the container usually could not be minimized because the walls of the container needed to be high enough to contain the splashing of the re-inking composition. This in turn resulted in the use of a container which was wider than necessary so that the ductor roll was in contact with the composition but not the walls of the container.
The changing viscosity of the re-inking composition can be compensated for to some extent by the use of an adjustment means which adjusts the gap between the ductor and the inking rollers. But, if the composition becomes too viscous, even the gap adjustment cannot provide sufficient compensation. When this happens, it becomes necessary to replace the composition with fresh re-inking liquid or to "thin-out" the composition in the reservoir by adding more vehicle or a solvent. Such a process can be messy when dealing with carbon compositions, and further is undesirable since it means a period of "down time" when the re-inking apparatus cannot be used.
Therefore, a need exists for an improved re-inking apparatus having an improved means for holding and recirculating the re-inking composition.